1. Field of the Invention
The present invention relates to an image evaluation apparatus and method for evaluating an image using a face included in the image. It also relates to a program for causing a computer to perform the image evaluation method.
2. Description of the Related Art
Recently, the wide spread use of digital cameras, along with a dramatic increase in the capacity of image recording media, has made it possible for users of digital cameras to record a large number of images on a single image recording medium. At the same time, this has caused the users troublesome efforts to select images to be processed from a huge number of images when, for example, placing a print order or the like. As such, in order to allow the users to efficiently select images, a function to make a short list of images based on certain conditions before the final decision for printing is made by the user or a function to select appropriate images for printing according to user preference is demanded.
For example, Japanese Unexamined Patent Publication No. 2002-010179 proposes a method in which an image is evaluated using one of image brightness, acceleration sensor output, and AF evaluation as the reference and an inappropriate image for printing is automatically excluded based on the evaluation result.
Further, Japanese Unexamined Patent Publication No. 2004-361989 discloses a method in which the orientation of a human face included in an image is determined, and an image evaluation value is calculated based on the determination result, then a desired image is selected from a plurality of images based on the calculated evaluation value.
Still further, U.S. Patent Application Publication No. 20020181784 discloses a method that evaluates an image using a comprehensive evaluation result, which is a summation of a plurality of evaluation items, including face proportion in the image, eye opening degree, face orientation, focus, image shake, image brightness, and the like.
Further, U.S. Patent Application Publication No. 20050089246 proposes a method in which a characteristic vector representing image quality is calculated for a face region included in an image, and the image quality of the face region is evaluated using the calculated characteristic vector.
As described above, many different types of image evaluation methods that perform image evaluation based on a face included in an image are proposed. The methods described in the aforementioned patent publications, however, perform image evaluation by simply calculating an evaluation value of each evaluation item. That is, the subjective evaluation of an image viewer is not necessarily reflected in the evaluation, so that there may be cases where the calculated evaluation differs from the evaluation of the image viewer.